Most modern academic historians will dispute this, because the prevailing view in the scholarly world is heavily influenced by various forms of historical determinism or materialism, which state that the great trends and currents of history are vast and old and unstoppable and largely beyond the ability of any one person or group to influence much one way or the other. From that point of view biography is history only in so much as it tells the story of a particular individual, but little more because, so the argument goes, even the great and the good are largely beholden to their circumstances and the socio-economic and other forces that really drive society and events. History then, so they say, is impersonal, and the old 'great man' theory is very much out of fashion.
Personally I think you need both to truly explain how things have happened the way they did - both the broader themes and forces, but also an understanding of the character, abilities and choices of particular important people. If for example the general form of the American presidency was always determined to develop in a certain way, nonetheless I think it matters that the first president was Washington and not, say, a more Napoleon-esque figure. The template for how one should conduct themselves as president, and how they should leave it, was set right from the start, and I think that had an influence that has endured. Equally if the US was destined for independence, and it probably was, a lesser general than Washington may have seen the colonies fail at the first attempt, and then who knows how things would ultimately have played out? In sum, ideally you need to approach things from as many angles as possible.
